Header image disappeared

My layer ID is #6234734 and I've made it viewable.

I've tried looking through the tutorials and FAQ's but have been unable to find a solution to my problem. For some reason, my header image seems to have disappeared. The image itself is on flickr and when I checked, it's still there and works perfectly fine. Right now, all that's visible is my journal title. How can I make the header image show up again? I didn't make any changes beforehand.